Question 162692
    Two airplanes leave Dallas at the same time and fly in opposite directions. One airplane travels at 80 miles per hour faster. After 3 hours they are 2940 miles apart. What is the speed of each airplane?
.
You will be applying the "distance formula":
d = rt
where
d is distance
r is rate or speed
t is time
.
Let x = speed of one plane
then because "One airplane travels at 80 miles per hour faster"
x+80 = speed of the other plane
.
"distance traveled by 1st plane" + "distance traveled by 2nd" = "distance apart"
3x + 3(x+80) = 2940 
dividing both sides by 3:
x + (x+80) = 980 
2x + 80 = 980
2x = 900
x = 450 mph (one plane)
.
2nd plane:
x+80 = 450+80 = 530 mph (2nd plane)